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<p>C++ includes support for two types of time manipulation:
</p>
<ul>
<li> The <code>chrono</code> library, a flexible collection of types that track time with varying degrees of precision (e.g. <span class="t-lc"><a href="chrono/time_point.html" title="cpp/chrono/time point">std::chrono::time_point</a></span>).
</li>
<li> C-style date and time library (e.g. <span class="t-lc"><a href="chrono/c/time.html" title="cpp/chrono/c/time">std::time</a></span>)
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<table id="toc" class="toc"><tr><td>
<div id="toctitle"><h2>Contents</h2></div>
<ul>
<li class="toclevel-1 tocsection-1">
<a href="chrono.html%23chrono_library"><span class="tocnumber">1</span> <span class="toctext">chrono library</span></a>
<ul>
<li class="toclevel-2 tocsection-2"><a href="chrono.html%23Duration"><span class="tocnumber">1.1</span> <span class="toctext">Duration</span></a></li>
<li class="toclevel-2 tocsection-3"><a href="chrono.html%23Clocks"><span class="tocnumber">1.2</span> <span class="toctext">Clocks</span></a></li>
<li class="toclevel-2 tocsection-4"><a href="chrono.html%23Time_point"><span class="tocnumber">1.3</span> <span class="toctext">Time point</span></a></li>
</ul>
</li>
<li class="toclevel-1 tocsection-5"><a href="chrono.html%23C-style_date_and_time_library"><span class="tocnumber">2</span> <span class="toctext">C-style date and time library</span></a></li>
<li class="toclevel-1 tocsection-6"><a href="chrono.html%23Example"><span class="tocnumber">3</span> <span class="toctext">Example</span></a></li>
</ul>
</td></tr></table>
<h3>
<span class="editsection">[<a href="http%3A//en.cppreference.com/mwiki/index.php" title="Edit section: chrono library">edit</a>]</span> <span class="mw-headline" id="chrono_library"><code>chrono</code> library</span>
</h3>
<p>The <code>chrono</code> library defines three main types (durations, clocks, and time points) as well as utility functions and common typedefs.
</p>
<h4>
<span class="editsection">[<a href="http%3A//en.cppreference.com/mwiki/index.php" title="Edit section: Duration">edit</a>]</span> <span class="mw-headline" id="Duration">Duration</span>
</h4>
<p>A duration consists of a span of time, defined as some number of ticks of some time unit.  For example, "42 seconds" could be represented by a duration consisting of 42 ticks of a 1-second time unit.
</p>
<table class="t-dsc-begin">

<tr class="t-dsc-header">
<td colspan="2"> <div>Defined in header <code>&lt;chrono&gt;</code> </div>
</td>
</tr>

<tr class="t-dsc-header">
<td colspan="2"> <div>Defined in  namespace <code>std::chrono</code> </div>
</td>
</tr>

<tr class="t-dsc-sep">
<td colspan="2">
</td>
</tr>
<tr class="t-dsc">
<td>  <div class="t-dsc-member-div">
<div><a href="chrono/duration.html" title="cpp/chrono/duration"> <span class="t-lines"><span>duration</span></span></a></div>
<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div>
</div>
</td>
<td>   a time interval  <br> <span class="t-mark">(class template)</span> 
</td>
</tr>
</table>
<h4>
<span class="editsection">[<a href="http%3A//en.cppreference.com/mwiki/index.php" title="Edit section: Clocks">edit</a>]</span> <span class="mw-headline" id="Clocks">Clocks</span>
</h4>
<p>A clock consists of a starting point (or epoch) and a tick rate.  For example, a clock may have an epoch of January 1, 1970 and tick every second.  C++ defines three clock types:
</p>
<table class="t-dsc-begin">

<tr class="t-dsc-header">
<td colspan="2"> <div>Defined in header <code>&lt;chrono&gt;</code> </div>
</td>
</tr>

<tr class="t-dsc-header">
<td colspan="2"> <div>Defined in  namespace <code>std::chrono</code> </div>
</td>
</tr>

<tr class="t-dsc-sep">
<td colspan="2">
</td>
</tr>
<tr class="t-dsc">
<td>  <div class="t-dsc-member-div">
<div><a href="chrono/system_clock.html" title="cpp/chrono/system clock"> <span class="t-lines"><span>system_clock</span></span></a></div>
<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div>
</div>
</td>
<td>   wall clock time from the system-wide realtime clock   <br> <span class="t-mark">(class)</span> 
</td>
</tr>

<tr class="t-dsc-sep">
<td colspan="2">
</td>
</tr>
<tr class="t-dsc">
<td>  <div class="t-dsc-member-div">
<div><a href="chrono/steady_clock.html" title="cpp/chrono/steady clock"> <span class="t-lines"><span>steady_clock</span></span></a></div>
<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div>
</div>
</td>
<td>   monotonic clock that will never be adjusted  <br> <span class="t-mark">(class)</span> 
</td>
</tr>

<tr class="t-dsc-sep">
<td colspan="2">
</td>
</tr>
<tr class="t-dsc">
<td>  <div class="t-dsc-member-div">
<div><a href="chrono/high_resolution_clock.html" title="cpp/chrono/high resolution clock"> <span class="t-lines"><span>high_resolution_clock</span></span></a></div>
<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div>
</div>
</td>
<td>   the clock with the shortest tick period available  <br> <span class="t-mark">(class)</span> 
</td>
</tr>
</table>
<h4>
<span class="editsection">[<a href="http%3A//en.cppreference.com/mwiki/index.php" title="Edit section: Time point">edit</a>]</span> <span class="mw-headline" id="Time_point">Time point</span>
</h4>
<p>A time point is a duration of time that has passed since the epoch of specific clock.
</p>
<table class="t-dsc-begin">

<tr class="t-dsc-header">
<td colspan="2"> <div>Defined in header <code>&lt;chrono&gt;</code> </div>
</td>
</tr>

<tr class="t-dsc-header">
<td colspan="2"> <div>Defined in  namespace <code>std::chrono</code> </div>
</td>
</tr>

<tr class="t-dsc-sep">
<td colspan="2">
</td>
</tr>
<tr class="t-dsc">
<td>  <div class="t-dsc-member-div">
<div><a href="chrono/time_point.html" title="cpp/chrono/time point"> <span class="t-lines"><span>time_point</span></span></a></div>
<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div>
</div>
</td>
<td>   a point in time  <br> <span class="t-mark">(class template)</span> 
</td>
</tr>
</table>
<h3>
<span class="editsection">[<a href="http%3A//en.cppreference.com/mwiki/index.php" title="Edit section: C-style date and time library">edit</a>]</span> <span class="mw-headline" id="C-style_date_and_time_library"><a href="chrono/c.html" title="cpp/chrono/c">C-style date and time library</a></span>
</h3>
<p>Also provided are the C-style date and time functions, such as <span class="t-lc"><a href="chrono/c/time_t.html" title="cpp/chrono/c/time t">std::time_t</a></span>, <span class="t-lc"><a href="chrono/c/difftime.html" title="cpp/chrono/c/difftime">std::difftime</a></span>, and <span class="t-lc"><a href="chrono/c/CLOCKS_PER_SEC.html" title="cpp/chrono/c/CLOCKS PER SEC">CLOCKS_PER_SEC</a></span>.
</p>
<h3>
<span class="editsection">[<a href="http%3A//en.cppreference.com/mwiki/index.php" title="Edit section: Example">edit</a>]</span> <span class="mw-headline" id="Example">Example</span>
</h3>
<div class="t-example">
<p> This example displays information about the execution time of a function call:
 </p>
<div class="t-example-live-link"><div class="coliru-btn coliru-btn-run-init">Run this code</div></div>
<div dir="ltr" class="mw-geshi" style="text-align: left;"><div class="cpp source-cpp"><pre class="de1"><span class="co2">#include &lt;iostream&gt;</span>
<span class="co2">#include &lt;chrono&gt;</span>
<span class="co2">#include &lt;ctime&gt;</span>
 
<span class="kw4">long</span> fibonacci<span class="br0">(</span><span class="kw4">int</span> n<span class="br0">)</span>
<span class="br0">{</span>
    <span class="kw1">if</span> <span class="br0">(</span>n <span class="sy1">&lt;</span> <span class="nu0">3</span><span class="br0">)</span> <span class="kw1">return</span> <span class="nu0">1</span><span class="sy4">;</span>
    <span class="kw1">return</span> fibonacci<span class="br0">(</span>n<span class="sy2">-</span><span class="nu0">1</span><span class="br0">)</span> <span class="sy2">+</span> fibonacci<span class="br0">(</span>n<span class="sy2">-</span><span class="nu0">2</span><span class="br0">)</span><span class="sy4">;</span>
<span class="br0">}</span>
 
<span class="kw4">int</span> main<span class="br0">(</span><span class="br0">)</span>
<span class="br0">{</span>
    <a href="chrono/time_point.html"><span class="kw835">std::<span class="me2">chrono</span><span class="sy4">::</span><span class="me2">time_point</span></span></a><span class="sy1">&lt;</span><a href="chrono/system_clock.html"><span class="kw847">std::<span class="me2">chrono</span><span class="sy4">::</span><span class="me2">system_clock</span></span></a><span class="sy1">&gt;</span> start, end<span class="sy4">;</span>
    start <span class="sy1">=</span> std<span class="sy4">::</span><span class="me2">chrono</span><span class="sy4">::</span><span class="me2">system_clock</span><span class="sy4">::</span><span class="me2">now</span><span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span>
    <a href="io/basic_ostream.html"><span class="kw1439">std::<span class="me2">cout</span></span></a> <span class="sy1">&lt;&lt;</span> <span class="st0">"f(42) = "</span> <span class="sy1">&lt;&lt;</span> fibonacci<span class="br0">(</span><span class="nu0">42</span><span class="br0">)</span> <span class="sy1">&lt;&lt;</span> <span class="st0">'<span class="es1">\n</span>'</span><span class="sy4">;</span>
    end <span class="sy1">=</span> std<span class="sy4">::</span><span class="me2">chrono</span><span class="sy4">::</span><span class="me2">system_clock</span><span class="sy4">::</span><span class="me2">now</span><span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span>
 
    <a href="chrono/duration.html"><span class="kw837">std::<span class="me2">chrono</span><span class="sy4">::</span><span class="me2">duration</span></span></a><span class="sy1">&lt;</span><span class="kw4">double</span><span class="sy1">&gt;</span> elapsed_seconds <span class="sy1">=</span> end<span class="sy2">-</span>start<span class="sy4">;</span>
    <a href="chrono/c/time_t.html"><span class="kw865">std::<span class="me2">time_t</span></span></a> end_time <span class="sy1">=</span> std<span class="sy4">::</span><span class="me2">chrono</span><span class="sy4">::</span><span class="me2">system_clock</span><span class="sy4">::</span><span class="me2">to_time_t</span><span class="br0">(</span>end<span class="br0">)</span><span class="sy4">;</span>
 
    <a href="io/basic_ostream.html"><span class="kw1439">std::<span class="me2">cout</span></span></a> <span class="sy1">&lt;&lt;</span> <span class="st0">"finished computation at "</span> <span class="sy1">&lt;&lt;</span> <a href="chrono/c/ctime.html"><span class="kw857">std::<span class="me2">ctime</span></span></a><span class="br0">(</span><span class="sy3">&amp;</span>end_time<span class="br0">)</span>
              <span class="sy1">&lt;&lt;</span> <span class="st0">"elapsed time: "</span> <span class="sy1">&lt;&lt;</span> elapsed_seconds.<span class="me1">count</span><span class="br0">(</span><span class="br0">)</span> <span class="sy1">&lt;&lt;</span> <span class="st0">"s<span class="es1">\n</span>"</span><span class="sy4">;</span>
<span class="br0">}</span></pre></div></div>
<p>Possible output:
</p>
<div dir="ltr" class="mw-geshi" style="text-align: left;"><div class="text source-text"><pre class="de1">f(42) = 267914296
finished computation at Mon Jul 29 08:41:09 2013
elapsed time: 0.670427s</pre></div></div> 
</div>

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